David Mitchell wrote:
> I wanted to use Varchar data via ODBC on Windows and Access. ddfet
> returns the variable length data as a boxed vector, but is too slow to
> be useful with large databases. ddfch returns Varchar data as Cx255
> matrix, efficient and fast, but not the form the data is stored in.
>
> Attached is a modified ddfchvc that returns two columns for each Varchar
> column. The first is the Cx255 text matrix. The second is the Cx1 list
> of lengths for each Varchar row. This allows the original data to be
> reconstructed while preserving the general result format of ddfch. The
> performance is comparable with ddfch, since the list of lengths must be
> created in either verb. The reconstruction of the variable length data
> as a vector of enclosed vectors can be done with something like:
>
I usually trim padding space if needed, but your idea sounds useful and
efficient. A less efficient but simplier approach is just replacing the line
(code not tested)
NB. z=. z,< n
if. _3 12 e.~ 6{i_index{ci do.
z=. z,< (0>.len) <@{.("0 1) n
else.
z=. z,< n
end.
--
regards,
bill
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